DIGITAL SUBSCRIBER LINE (DSL) ADVANCES

Prepared by,

Pow Jun Jiang (EE 071271)

What is DSL??? A modem technology that uses existing

twisted-pair telephone lines to transport high-bandwidth data

Run on regular copper phone wires which is a direct dedicated connection between PC and the phone company central office

Make use of previously unused bandwidth on the phone line

Figure 1: General Overview of DSL

Figure 2: Signals in Copper Phone Line

Basic Requirements Require 10BaseT Ethernet card Basic home DSL lines can connect to

regular analog phones to RJ-11 jacks POTS (Plain Old Telephone Service)

splitter can also be used.

Advantages Fast Doesn’t tie up to phone line Always on Reliable Use the phone line A router, with DSL modem, allows up to

eight computers to access the Internet over a single DSL line.

Far cheaper Flexible and scalable, ideal for growing

business computer networks Enable users to work from home, listen to

streaming audio or watch streaming video while working on your computer.

Disadvantages DSL connection works better when user is

closer to the provider's central office The connection is faster for receiving data

than it is for sending data over the Internet The service is not available everywhere

Network Access Provider Benefits Do not need to install more copper or lay down

miles of expensive fiber Eliminate providers' need to constantly upgrade

their pricey Class 5 switch installations DSL bypasses the Class 5 switch for data-only

calls, so access providers can accept more traffic without investing in a huge switch upgrade

Voice and data paths are separated

By keeping costs low, service providers can make money off the traditionally low-margin business of providing Internet access.

DSL User Benefits Can experience high-speed Web browsing and

can send and receive large documents Provide a cost-effective way for telecommuters

and branch offices to access the corporate network, provisioned via secure virtual private network services

Improve the quality and reduce the cost of communications among employees via videoconferencing

Types of DSLAsymmetrical DSL (ADSL) offers high-speed digital service and analog voice

service over a local loop. An ADSL line is for the exclusive use of each

customer so there is no contention for bandwidth on that loop.

ADSL transfers data as far as 18,000 feet over copper wire at a rate of 7 Mbps on the downlink and 1 Mbps on the uplink.

High Bit Rate DSL (HDSL) Provide for T1 service on copper wire. Deliver T1 service at a DS1 rate over a

four-wire loop of two twisted pairs. Most established DSL technologies Offer full duplex speeds at a DS1 (1.544

Mbps) rate or 2Mbps over 3 phone lines. Transfer data up to 12,000 feet (can be

longer if repeatered).

High Bit-Rate DSL II (HDSL II) Offer the same performance as HDSL, but over a

single phone line.

ISDN DSL (IDSL) Hybrid of DSL and ISDN technologies Used for long duration Internet and remote Local

Area Network (LAN) access. Dedicated to data – does not support switched

voice service. Same data encoding technique as of ISDN

devices

Offers full duplex speed of 128 Kbps. Transfer data up to 18,000 feet.

Symmetric DSL (SDSL) Non standard version of HDSL with Plain Old

Telephone Service (POTS). Forerunner to HDSL II. Can be done using only one phone line Full duplex rates are limited to 384 Kbps for an

18,000-foot loop. DS1 speeds can be reached on a shorter (10,000-foot) loop.

Very high bit-rate DSL (VDSL) Faster cousin of ADSL. VDSL provides for the

transmission over copper of both digital data and analog voice.

Currently fastest DSL technology Currently in its experimental phase. VDSL works at speeds as high as 52 Mbps down

and 1.5 to 2.3 Mbps up. VDSL operates over much shorter distances,

achieving top speed over only 1000 feet of copper wire.

Rate Adaptive Asymmetric Digital Subscriber Line (RADSL)

Operates at the same bandwidths as ADSL. Additional capability of adjusting

bandwidth to the quality of the phone line during the data transmission, instead of just once at the start of the connection.

Up to 7Mbps downstream and up to 1.5 Mbps upstream.

Equipment Description

Plain Old Telephone Service (POTS) Splitter

Enables analog voice services to be carried simultaneously on the same line as digital data services. Allows the voice signal to be routed to the existing voice switch.

DSL Modem DSL transmission unit that engages in physical layer negotiations between the remote location and the CO.

DSL Access Multiplexer (DSLAM)

Aggregates DSL-based signals.

Element Management System

Hardware and software that make remote access and management possible

Provider Equipment

Consumer EquipmentEquipment Description

Network Interface Card (NIC)

Electronic circuitry that connects a workstation (computer) the network. Works to transmit and receive messages.

DSL Modem DSL transmission unit that engages in physical layer negotiations between the remote location and the CO

POTS Splitter Enables analog voice services to be carried simultaneously on the same line as digital data services. Allows the voice signal to be routed to the existing voice switch.

Network Interface Device (NID)

Device wired between a telephone protector and the interior customer wiring to isolate customer equipment from the network.

Figure 3: DSL Network Architecture

Figure 4: Single Computer Connection

Figure 5: Multi Computer Connection

Figure 6: Multiple Computers with Software Proxy Server

Figure 7: Multiple Computers With Router/ Firewall

Figure 8: Multiple Computers Using A Routed Subnet

Asymmetric DSL (ADSL) ADSL is a new broadband communication

technology that creates high-speed access to the Internet and remote networks using the phone lines that are already present in your home. ADSL is superior to analog modems in many respects.

DSL’s Speed Full-rate ADSL has the potential to deliver data at

speeds up to 8 Megabits per second G.Lite ADSL can deliver up to 1.5 Megabits per

second during downloads. This is 25 times faster than a 56K modem, and 50 times faster than a 28.8K modem!

Service providers will also offer slower rates (from 256 Kbps and up) at lower costs

Types of ADSL Full-rate ADSL Universal ADSL (G.lite)

Full-rate ADSL Data rates ranging from 1.5 to 8 Mbps

“downstream” from the Internet “Upstream” data rates from PC to the

Internet are as high as 1 Mbps Potential data rates decrease with increased

distance from the phone company’s CO (central office)

Costs for the service are more expensive than “G.Lite” ADSL

G.Lite ADSL G.Lite ADSL is a scaled-down version that

delivers up to 1.5 Mbps downstream and 384 Kbps up

Service providers will offer slower rates for lower prices

Less expensive than full-rate ADSL Easier to install

Splitter vs. Splitterless Full-rate ADSL requires that a device, known as a

splitter, be installed on the phone line where it enters a home in order to separate the voice service from the data service

G.Lite ADSL will not usually require a splitter, although some homes with problematic wiring or certain types of telephones will require one.

DSL In Malaysia

"tmnet streamyx" service is supported by DSL Types of DSL technology chosen to support

tmnet streamyx are ADSL, SDSL and GLite DSL An ADSL system basically consists of two parts

i.e. the Central Office (CO) which is located at the exchange building and the other, Remote Termination Unit (RTU) at subscriber's premise which are connected via an existing pair of copper telephone lines.

Figure 9: TM Net Streamyx Basic Network Configuration

The Central Office (CO) for ADSL consists of two types of chassis.

The first chassis is the ADSL unit for modem cards and control card while the second chassis is for the POTS (Plain Old Telephone Service) splitter.

The Remote Terminal Unit (RTU) for ADSL also consists of POTS splitter and ADSL modem.

Conclusion ADSL provides a new way to use

existing phone lines. It’s faster! It’s always on! Voice and data on one line at the

same time! ADSL is the best way to get online!